<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>点我</button>
    <script>
        var btn = document.querySelector("button")
        //使用JS代码来设置
        btn.dataset.index = "1"
        //使用JS来获取
        console.log(btn.dataset.index);
    </script>
</body>
</html>